1. Field of the Invention
The present invention relates to a power saving method for a User Equipment (UE) in a wireless communication system. More particularly, the present invention relates to a power saving method for a User Equipment (UE) supporting enhanced Inter-Cell Interference Coordination/Time-domain ICIC (eICIC/Time-domain ICIC) in a wireless communication system.
2. Description of the Related Art
Mobile communication systems were initially developed to provide a subscriber with voice communication services while the subscriber was on the move. With advances in communication and related technologies, mobile communication system have evolved to support high speed data communication services as well as the standard voice communication services.
Recently, as a next generation mobile communication system, Long Term Evolution (LTE) is being standardized by the 3rd Generation Partnership Project (3GPP). LTE is a technology designed to provide high speed packet-based communication of up to 100 Mbps. Unlike the standard voice service, most data services are allocated resources according to the amount of data to be transmitted and the condition of the channel. Accordingly, in a wireless communication system such as a cellular communication system, it is important to manage resource allocation based on the resource scheduled for data transmission, channel condition, and amount of data to be transmitted. This is a requirement even in the LTE system as a next generation mobile communication system, and the scheduler located at the enhanced Node B (eNB) manages and assigns radio resources. Recent studies are focused on the LTE-Advanced (LTE-A) for improving data rate with the adaptation of several new techniques of the legacy LTE system.
For such an advance in technology, Inter-Cell Interference Coordination (ICIC) is also evolving to enhanced ICIC (eICIC) or Time-domain ICIC. The eICIC/Time-domain ICIC is a technique to mitigate inter-cell interference by reducing transmit power in a cell causing interference or by muting data transmission in units of subframe.
A UE located in a corresponding cell can have an opportunity for channel measurement to maintain a radio link and transmit data in the corresponding subframe. This subframe is referred to as an Almost Blank Subframe (ABS) and appears in a predetermined pattern. That is, since interference causes reduction in the transmit power or stops data transmission in ABS, the UE located in the neighbor cell can perform various operations without interference from the interference-causing cell. With the use of ABS, the UE is restricted of serving cell and neighbor cell measurements and channel measurement for Channel Quality Information/Channel Status Information (CQI/CSI) report to the serving cell in units of subframe and thus the information on the subframe pattern per purpose is sent to the UE through Radio Resource Control (RRC) signaling. The eICIC/Time-domain ICIC is actively discussed to improve the power saving efficiency. Therefore, a need exists for an apparatus and a method for conserving power of the UE supporting the eICIC/Time-domain ICIC.